drm/vmwgfx: Unreserve BO on error

Unlock BOs in reverse order.
Add an acquire context so that lockdep doesn't complain.

Fixes: d6667f0 ("drm/vmwgfx: Fix handling of dumb buffers")
Signed-off-by: Ian Forbes <ian.forbes@broadcom.com>
Signed-off-by: Zack Rusin <zack.rusin@broadcom.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241210195535.2074918-1-ian.forbes@broadcom.com

drivers/gpu/drm/vmwgfx/vmwgfx_kms.c

@@ -750,6 +750,7 @@ vmw_du_cursor_plane_atomic_update(struct drm_plane *plane,
 	struct vmw_plane_state *old_vps = vmw_plane_state_to_vps(old_state);
 	struct vmw_bo *old_bo = NULL;
 	struct vmw_bo *new_bo = NULL;
+	struct ww_acquire_ctx ctx;
 	s32 hotspot_x, hotspot_y;
 	int ret;
 
@@ -769,19 +770,26 @@ vmw_du_cursor_plane_atomic_update(struct drm_plane *plane,
 	if (du->cursor_surface)
 		du->cursor_age = du->cursor_surface->snooper.age;
 
+	ww_acquire_init(&ctx, &reservation_ww_class);
+
 	if (!vmw_user_object_is_null(&old_vps->uo)) {
 		old_bo = vmw_user_object_buffer(&old_vps->uo);
-		ret = ttm_bo_reserve(&old_bo->tbo, false, false, NULL);
+		ret = ttm_bo_reserve(&old_bo->tbo, false, false, &ctx);
 		if (ret != 0)
 			return;
 	}
 
 	if (!vmw_user_object_is_null(&vps->uo)) {
 		new_bo = vmw_user_object_buffer(&vps->uo);
 		if (old_bo != new_bo) {
-			ret = ttm_bo_reserve(&new_bo->tbo, false, false, NULL);
-			if (ret != 0)
+			ret = ttm_bo_reserve(&new_bo->tbo, false, false, &ctx);
+			if (ret != 0) {
+				if (old_bo) {
+					ttm_bo_unreserve(&old_bo->tbo);
+					ww_acquire_fini(&ctx);
+				}
 				return;
+			}
 		} else {
 			new_bo = NULL;
 		}
@@ -803,10 +811,12 @@ vmw_du_cursor_plane_atomic_update(struct drm_plane *plane,
 						hotspot_x, hotspot_y);
 	}
 
-	if (old_bo)
-		ttm_bo_unreserve(&old_bo->tbo);
 	if (new_bo)
 		ttm_bo_unreserve(&new_bo->tbo);
+	if (old_bo)
+		ttm_bo_unreserve(&old_bo->tbo);
+
+	ww_acquire_fini(&ctx);
 
 	du->cursor_x = new_state->crtc_x + du->set_gui_x;
 	du->cursor_y = new_state->crtc_y + du->set_gui_y;